The present invention relates to a method and a device for estimating the total weight of an automobile vehicle.
The knowledge of the total weight of an automobile vehicle is needed for the correct operation of numerous devices onboard the vehicle, notably the devices for managing braking, for managing an automatic transmission or for managing the stiffness of the suspensions. Indeed, the greater the load of the vehicle, the stiffer the suspensions become in order to ensure the comfort and the safety of the passengers. Furthermore, for utility vehicles offering a high loading capacity, an estimation of the weight of the vehicle allows the user to guarantee compliance with the total laden weight authorized.
It is therefore desirable to obtain a quick and reliable estimation of the weight of the vehicle.
Today, the estimation of the weight of an automobile vehicle may be carried out in various ways, for example by a direct measurement of the weight by means of sensors for displacement of the suspensions and using the knowledge of the stiffness of the shock absorbers. However, these methods are expensive because they require the installation and the calibration at the factory of displacement sensors. Moreover, the dispersion in manufacturing and in aging of the stiffness of the suspensions does not allow a precise estimation of the weight to be obtained.
There also exist methods for estimation of the weight of an automobile vehicle by application of the fundamental principle of dynamics.
In this respect, reference may be made to the document U.S. Pat. No. 6,249,735 which describes a method for estimating the state of loading of a vehicle as a function of the measured torque of the engine and of the acceleration of the vehicle calculated by discrete approximation of the derivative of the speed and by filtering. Such a method does not allow a sufficiently reliable and robust estimation of the weight.
Reference may also be made to the document FR 2 857 090 which describes a method for estimating the weight based on a recursive least-squares algorithm using the acceleration of the vehicle. However, such an estimation method does not allow a quick estimation of the weight of the automobile vehicle.
Moreover, the methods for estimating the weight of an automobile vehicle by application of the fundamental principle of dynamics at a single moment in time are particularly imprecise and onerous to implement because they require an estimation of numerous parameters of the vehicle and are based on assumptions which are not always verified, such as a zero wind speed, an inclination of zero, etc.
Furthermore, in some current vehicles, the user must press a control button when the vehicle is loaded. The control button will subsequently activate a program for controlling the processor of the automatic transmission adapted to a loaded or unloaded vehicle, referred to as “nominal”. However, the installation of such a control button is relatively costly.
However, none of these documents allows it to be defined quickly whether the vehicle is lightly or heavily loaded, and hence to determine a given interval of weight of the vehicle, without determining its exact value.